The present invention relates to an apparatus for monitoring fuel within a fuel delivery system of a motor vehicle, and more particularly, to a fuel quality sensor associated with a housing in a fuel delivery system for measuring a characteristic corresponding to fuel quality.
Fuels for internal combustion engines are composed of a mixture of hydrocarbon compounds and various additives that can be included for improving the properties. Modern internal combustion engines are capable of processing fuels of differing quality, which can be a result of various additives and hydrocarbon compounds in the fuel. For example, the operational characteristics of an internal combustion engine will vary depending on the proportion of the different hydrocarbons in the fuel. Thus, automotive manufacturers desire to monitor fuel quality.
Fuel quality is known to vary as a measure of impedance and temperature. A fuel composition sensor responsive to the dielectric constant of a mixture of two fuel components generates a fuel composition signal indicating the relative concentration of the two fuels. A capacitive sensor is known where the fuel mixture to be sensed forms the dielectric between capacitor plates. If one of the fuels has a significant variation of dielectric constant with temperature, the output signal of such a sensor may vary with fuel temperature at high concentrations of the one fuel. The output of a capacitive sensor for a fuel mixture of gasoline and methanol becomes significantly more dependent on fuel temperature as the concentration of methanol increases. Therefore, it is known to include a fuel temperature sensor in the same package so that the fuel composition sensor output can be corrected for fuel temperature as required.
Known sensors will usually fail by shorting to one of the power supply terminals where constant limit references can be acceptable to signal sensor failure. However, contaminated fuel may not produce the same failure mode. In particular, the contaminated fuel can produce an output voltage, outside the expected voltage range at a particular fuel temperature, but not at or near either of the voltage supply voltages.
According to the present invention, the sensor is incorporated into the housing of a fuel pressure regulator or accumulator or any other fuel delivery controlling, sensing, or handling device in the fuel handling system, thereby reducing the number of connections required in the fuel system from a stand alone sensor. This configuration also reduces the total under hood volume required when compared to discrete components. The present invention provides a compact low cost package for a fuel sensor. The present invention reduces the number of connections required in the fuel system. In the preferred embodiment, the sensor is mounted in close proximity to the fuel injectors. The sensor according to the present invention measures impedance and temperature in a single sensor package. The sensor uses two or more plates spaced from one another by a gap of approximately 0.5 mm to approximately 1.0 mm and measures impedance across the gap(s), while a temperature sensor incorporated into the package measures the temperature. An apparatus according to the present invention monitors a fuel quality characteristic with a combined impedance and temperature sensor mounted within a fuel delivery system having a fuel pressure regulator and/or an accumulator. The combined impedance and temperature sensor is housed within either the fuel pressure regulator or the accumulator for measuring a characteristic corresponding to fuel quality. Fuel quality is known to vary as a function of impedance and temperature.
An apparatus according to the present invention monitors fuel quality within a fuel delivery system of a motor vehicle. The apparatus includes a housing associated with at least one of a fuel pressure regulator and an accumulator. A sensor is supportable by the housing to be exposed to fuel passing through the fuel delivery system of the motor vehicle for measuring at least one characteristic of fuel corresponding to fuel quality. The apparatus can include a fuel rail assembly connectable to the fuel delivery system of the motor vehicle, where the fuel rail assembly includes a pressure regulator and an accumulator. According to the present invention, a sensor is associated with the fuel rail assembly for measuring at least one characteristic of fuel quality of fuel passing through the fuel rail. In the preferred configuration, the sensor includes a pair of plates spaced from one another by a gap of between approximately 0.5 mm to approximately 1.0 mm inclusive for measuring impedance across the gap.
Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.